Improvement And Mechanism Of Short-clustered Maltodextrin On Frozen Dough Quality

The advent of frozen dough technology has spurred the industrialization of the baking sector and the transformation of the brand chain management model.The deterioration of dough quality during frozen storage,mainly manifested by the decrease in dough gassing power and gas retention capacity,is the key factor restricting its further development.Incorporating improvers is the most effective and successful way to improve the frozen dough quality.Maltodextrin has been widely applied in the quality improvement of frozen food due to its ability to lower the freezing point and maintain the system stability,however,its functionality in frozen dough has yet to be explored.High-branched polymers play an important role in the cryopreservation of biologics due to their unique branching structure.So based on the design of fine structure,the utilization of maltodextrin additives may be a feasible strategy to improve the quality of frozen dough.Nevertheless,the effects and regulation mechanism of structure-oriented maltodextrin on the frozen dough quality are still not understood.Therefore,in this paper,maltodextrin with different fine structures was firstly applied to frozen dough,and then the influences on the quality of frozen dough were systematically analyzed,further,the structure-function relationships among fine structure,icerecrystallization-inhibition(IRI)activity and dough quality were explored.Then,using the short-clustered maltodextrin(SCMD)derived from glycosidic bond reconstruction as the research object,the dose-effect relationship was further explored,and the key factors of SCMD regulating the frozen dough quality were determined.The mechanism of SCMD improving the frozen dough quality was deeply analyzed from three perspectives,namely,regulating the ice-water state,alleviating the cold denaturation of gluten protein and enhancing the frost resistance of yeast,which will provide novel insights into the improvement of frozen dough quality and the design of multi-functional maltodextrin.The main research contents and results are as follows:(1)Five kinds of maltodextrins with different fine structures were studied,fine structures were characterized,IRI activity was determined by the “splat” method,and improvement effects on the frozen dough quality were evaluated.The structure-function relationships among fine structure,IRI activity and frozen dough quality were systematically analyzed.Results showed that the branching degree,average chain length and relative molecular weight of maltodextrin increased nonlinearly with the decrease of DE value.However,the size of ice crystals formed by maltodextrin solution decreased gradually,and the IRI activity increased.Further evaluation of the frozen dough quality showed that the addition of high-DE-value maltodextrin(DE 12 maltodextrin)significantly accelerated the gas production rate of dough,weakened the stability of frozen dough system,and led to a decrease in the specific volume of bread.The addition of low-DE-value maltodextrin(DE 2 maltodextrin)was more conducive to maintaining the relative balance between gassing power and gas retention capacity of dough,improving the texture quality of frozen dough bread.Compared with common maltodextrin with the similar DE value,the addition of SCMD derived from glycosidic bond reconstruction could reduce the loss of bound water in dough more effectively,and further improve the stability of frozen dough system,finally improving the baking quality of frozen dough.Analysis of the structure-function relationship showed that the IRI activity of maltodextrin was positively correlated with the branching degree and average chain length,but negatively correlated with the DE value.The branching and polymerization degrees of maltodextrin significantly affected the moisture state of dough and were proved to be key factors affecting the texture quality of frozen dough bread.Among the five maltodextrins in this paper,SCMD exhibited the most significant improved effect on frozen dough quality.(2)Further,the dose-effect relationship between SCMD dosage and frozen dough quality was investigated,and the key factors of SCMD regulating the frozen dough quality were determined.The results of water state analysis showed that the addition of SCMD could inhibit the loss of bound water and reduce the freezable water content,and the most significant change was observed when the addition amount was increased from 0.5% to 1%.Results of the elastic modulus,the content of free sulfhydryl group and the gluten network structure of dough showed that 1% and 2% SCMD effectively delayed the break of disulfide bonds,slowed the decline of dough elastic modulus,and kept the gluten network relatively compact and continuous after 8-week frozen storage.Further analysis of the yeast survival rate,yeast growth curve and gas production rate of dough showed that the addition of SCMD significantly improved the yeast survival rate,and after 8-week frozen storage,compared with the control group,the gas production rates of dough with 0.5%,1% and 2% SCMD added were increased by 19.7%,49.1% and 54.5%,respectively.Finally,the texture quality of frozen dough bread was evaluated,and it was found that 1% SCMD had a more significant effect on the specific volume and hardness of frozen dough bread,and the bread inside was more porous.However,when the addition amount was increased to 2%,the texture quality of bread was not further improved significantly.In summary,the moisture state,gluten network structure and yeast activity were closely related to improved effects of SCMD on the frozen dough quality,and the subsequent mechanism study was conducted under the 1%supplemental amount of SCMD.(3)Based on the high IRI activity of SCMD,the mechanism of SCMD improving the quality of frozen dough was systematically analyzed from the perspective of regulating the ice-water state of dough,compared with trehalose(TH)and guar gum(GUAR)whose interaction with water molecules were different.Firstly,the protective effects of three saccharide-based compounds on the frozen dough quality were evaluated.SCMD,TH and GUAR all increased the gas production rate of dough after 8-week frozen storage.The addition of SCMD and TH improved the dough viscoelasticity and promoted the relative balance between gas production and gas retention of dough.Subsequently,the effects of three saccharide-based compounds on the dough water state and their stability of binding to the ice surface were analyzed.Results showed that they mainly changed the content of weakly bound water in doughs.There was no significant difference in binding stability to the ice crystal surface between SCMD monomer and TH,and GUAR monomer was the worst.Based on the above results,it was speculated that SCMD hindered the formation of ice crystals through steric hindrance and hydrogen bond interaction,and further inhibited ice recrystallization by stably binding to ice crystal surface.The unique short-clustered structure of SCMD made it better than TH and GUAR in improving the frozen dough quality.SCMD supplementation was observed to counteract the breakdown of gluten network and the decrease in yeast activity.However,effects on the molecular levels of gluten protein and yeast are yet to be determined.(4)Taking into account that gluten was a key factor influencing the ice-water state of dough,gluten was isolated from the dough and then recombined with SCMD to analyze the alterations in hydration characteristics and conformational behavior of gluten during frozen storage,the molecular mechanism of SCMD alleviating the cold denaturation of gluten was explored.Results showed that with frozen storage extending,the integrity and continuity of gluten network decreased,resulting in poor hydration ability and loss of bound water.In addition,the surface hydrophilicity of gluten protein was weakened and hydrophobicity was enhanced.Upon frozen storage,the α-helical shifted to β-folding and β-turning structures due to the rise in enthalpy of the system caused by the formation of extra hydrogen bonds between the α-helical and water molecules,causing the protein to unfold.The recombinant gluten protein added with SCMD was further analyzed,results showed that after 8-week frozen storage,compared to the Control group,the order and integrity of gluten network increased,and the content of weakly bound water in gluten protein was significantly increased,indicating that SCMD addition could effectively alleviate the deterioration of gluten network structure and the loss of bound water during frozen storage.In addition,compared with the Control group,SCMD supplementation significantly reduced the exposure of hydrophobic amino acid residues,increased the surface hydrophilicity and decreased the hydrophobicity of frozen gluten protein.Further conformational behavior analysis showed that the addition of SCMD effectively restricted the transformation of α-helix to β-folding and β-turning structures in the protein.After 4-week and 8-week frozen storage,the α-helix content of SCMD protein was increased by 17.0% and 25.7%,respectively,compared with the Control protein.Results of molecular dynamics simulation showed that the short-clustered structure could more effectively weaken the protein-water interaction at low temperatures by forming more hydrogen bonds with water molecules,and based on steric hindrance effect,reducing the enthalpy driving force and inhibiting the conformational transformation of proteins,alleviating the cold denaturation of gluten proteins.(5)Based on the important role of yeast in the gassing power of dough,the molecular mechanism of SCMD enhancing the frost resistance of yeast was further explored.Effects of SCMD addition on yeast intracellular metabolism and cell membrane homeostasis under high ice-crystal stress were evaluated.Results indicated that the survival rate and defrosting activity of yeast in the SCMD group were superior to those of the other groups.Metabolomics analysis revealed significant differences in the intracellular metabolic pattern of yeast between the SCMD group and the control groups.The addition of SCMD enhanced lipid metabolism,regulated amino acid metabolism and energy metabolism,making the physiological state of yeast more inclined to frozen semi-dry yeast that did not suffer icecrystal stress.In addition,compared with the negative control group,the ultrastructure of yeast in the SCMD group was relatively intact,the membrane integrity and fluidity were increased,indicating the damage of ice recrystallization to yeast was decreased with the existence of SCMD.Further exploration of glycerophospholipid metabolism showed that the relative abundances of lipid molecules containing unsaturated and short-chain fatty acids in the SCMD yeast were higher than those in the negative control yeast,which was consistent with results of the enhanced fluidity of cell membrane.Molecular simulations demonstrated that SCMD monomer could facilitate the motion of phospholipid molecules at low temperatures and bolster the stability of phospholipid bilayers when the temperature fluctuated.It was speculated that SCMD could create a “micro-water” environment by interacting with ice-water molecules around yeast,which reduced the ice-recrystallization pressure and changed the intracellular metabolism mode and the physiological characteristics of cell membranes of yeast,maintaining the cell membrane homeostasis of yeast during frozen storage and thawing,thus the yeast survival rate and the activity as well as fermentation ability of the thawed yeast were improved.